The present invention relates generally to a method and apparatus for data migration in a storage system. More particularly the present invention relates to a method and apparatus for virtualizing network storage of existing storage devices after migrating the existing storage devices to a new storage system.
Data migration is the process of transferring data from an old storage system to another while data stored in the old storage system remain accessible. Data migration has become popular with computer users because it allows for storage system replacements with minimum impact on services. Data migration is well known in the art and is available, for example, from Hitachi Data Systems of Santa Clara, Calif.
“Remote copy” is a mirroring technology that involves the copying of data from a local site to a remote site for back-up purposes. Typically, remote copy is done in real-time to provide continuous data protection, and thereby minimize data loss in the event of a disaster such as a storage system crash or unscheduled facility shutdown (e.g., due to fire, earthquake, power loss, etc.). Remote copy software and associated apparatus have been developed for backing-up the storage systems of a local mainframe computer using remote storage systems.
Users who have already implemented remote copy face a dilemma when replacing their storage systems during a data migration. On the one hand, these users typically have a need to upgrade their old storage systems in order to take advantage of the faster speed and higher capacity of newer storage systems. On the other hand, they cannot afford to disrupt their existing remote copy functions, and risk the possibility of data loss, during the data migration process. Because currently available techniques for performing data migration require that the remote copy function be stopped for long periods of time and/or reconfigured after the migration (which also takes a long time because the remote copy has to start over from an initial copy), most users do not have a choice but to risk data loss during the migration process. Further, a considerable investment may have been made in the old storage devices thus making it advantageous if these assets can continued to be used after data migration.
From the foregoing, a technique for performing data migration with minimum impact on remote copy and that can continue the use of the old storage devices after data migration is highly desirable.